Various mechanical and electronic ice bank controls are known in the prior art for maintaining a desired thickness of ice on a refrigerant evaporator coil. Such ice banks are primarily used in the beverage industry for providing a cooling source for dispensed soft drinks. Mechanical and electronic controls are known for maintaining the ice within a range of desired thickness. Electronic controls typically use a pair of probes suspended in a water bath adjacent the evaporator coils for determining the electrical resistance there between. Such probes take advantage of the fact that there exists a substantial conductivity difference between liquid water and ice. Thus, the cooling of the evaporator coil can be controlled in accordance with the sensed presence of liquid water or ice.
It is also well known that water varies greatly as to its conductivity depending on the source thereof. Various strategies have been employed to take into account this variation in water conductivity so that an ice bank can be formed of consistent size regardless of the water condition. Such a strategy can involve the use of two pairs of probes, one pair positioned so they remain continually in liquid water using these probes to generate this reference value, and the second pair for determining the ice bank size. In the interest of reduced cost and complexity, it would be very desirable to provide for such a reference value and for ice bank sensing from a single pair of probes.